Collector structure of traveling wave tube

ABSTRACT

A collector of a traveling wave tube in which a larger quantity of loss ceramic members are arranged between an outer collector enclosure and an outer surface of a collector electrode for increasing high frequency loss to prevent RF leakage from the collector lead wire. The collector includes a collector electrode  2,  heat conductive columnar ceramic elements  3,  an outer collector enclosure  4  for maintaining vacuum and loss ceramic members  5  arranged between the outer surface of the collector electrode  2  and the inner surface of the outer collector enclosure  4.

FIELD OF THE INVENTION

[0001] This invention relates to a collector of a traveling wave tube.

BACKGROUND OF THE INVENTION

[0002] FIGS. 4 to 6 are longitudinal cross-sectional view of aconventional traveling wave tube. Specifically, FIG. 4 shows aconduction cooling type, FIG. 5 a forced air-cooling type and FIG. 6shows a water-cooling type.

[0003]FIG. 7 shows a longitudinal cross-sectional view of a conventionalcollector, while FIG. 8a is a transverse cross-sectional view of anotherillustrative structure of a conventional collector and FIG. 8b is alongitudinal cross-sectional view of FIG. 8a. FIG. 9 shows a two-stageversion of the collector shown in FIG. 8. Specifically, FIGS. 9a and 9 bare a transverse cross-sectional view and a longitudinal cross-sectionalview of the collector, respectively.

[0004] Among the devices which effect amplification of the micro-wave,using an electron beam, there is a traveling wave tube used as a relaystation for micro-waves and for satellite communication.

[0005] Referring to FIGS. 4 to 6, a traveling wave tube includes anelectronic gun 23 for radiating an electron beam 24, a delay wavecircuit 25 for producing interaction between the electron beam 24 andthe input micro-wave, a collector 26 for collecting the electron beam 24and a beam converging device 27 for converging the electron beam 24.

[0006] The electron beam 24 emitted by the electronic gun 23 traversesthe delay wave circuit 25 to amplify a signal and collected by thecollector 26. At this time, the electron beam 24 captured by thecollector 26 has its kinetic energy converted into thermal energy toraise the temperature of a collector electrode 28.

[0007] For this reason, the heat generated in the collector electrode 28needs to be released to outside. Among the methods for releasing theheat, there are a conduction cooling type collector 31 for releasing theheat from a base plate 30 to a heat sink 29, as shown in FIG. 4, aforced air-cooling type collector 33 by providing a fin 32 on the outerperiphery of the collector for flowing air thereon to release the heat,as shown in FIG. 5, and a water-cooling type collector 35 by providing awater-cooled pipe passed through by water to release the collector heat,as shown in FIG. 6.

[0008] For increasing the efficiency of the traveling wave tube, amethod known as collector potential lowering method is used. This methodconsists in progressively lowering the potential applied across thecollector electrode 28 relative to the delay wave circuit 25 to lowerthe speed of the electron beam 24 colliding against the collector todecrease the energy generated in the collector electrode 28. To thisend, there is provided a cylindrical ceramic element 36 for maintaininginsulation between the collector 26 and the delay wave circuit 25against high voltage.

[0009] Referring to FIG. 7, the collector structure of a conventionaltraveling wave tube includes an insulating enclosure 37 of ceramics etc.for insulating the collector electrode 28, formed of copper, molybdenumor graphite etc., for maintaining vacuum and air-tightness, a base plate30 for supporting the collector electrode 28 and passing heat generatedin the collector electrode 28 through the insulating member to releaseheat to outside and a cylindrical ceramic element 36 for maintaininginsulation against the delay wave circuit. These component parts areusually connected together by brazing or welding etc. This structure istermed an external insulation type collector 38.

[0010] In the above-described collector, there are occasions where thecollector electrode is displaced in the axial direction due tomechanical vibrations or impact. This positional deviation occasionallyleads to changes in the colliding position of the electron beam toevolve gases or to lead to an increased amount of retrogressiveelectrons to increase the helical current of the traveling wave tube,occasionally leading to destruction of the tube bulb.

[0011] Also, in such collector structure, there is raised a problem thatRF components (TEM mode) of the electron beam incident on the collectoris subjected to RF leakage through a collector lead line.

[0012] In JP Patent Kokai JP-A-2-101454 (1990), there is shown astructure in which the collector electrode 28 is supported by pluralheat-conductive columnar ceramic elements 40 arranged between thecollector electrode 28 and the external enclosure 41 to improvevibration-proofness and resistance against impact, while maintainingvoltage withstand characteristics, as shown in FIGS. 8a and 8 b. Thisstructure is termed an internal insulation type collector 39.

[0013] In this type of the collector, the outer enclosure 41, collectorelectrode 28 and the highly heat-conductive columnar ceramic elements 40are secured in position by deforming the outer enclosure 41 such as bypress-working. If, in this structure, plural collector electrodes 28,specifically a first collector electrode 42 and a second collectorelectrode 43, are used and arranged in this order from the upstream tothe downstream side of the electron beam, it is possible to lower thepotential of the second collector electrode 43 relative to the firstcollector electrode 42 to improve the overall efficiency of thetraveling wave tube.

[0014] A two-stage collector 44 is illustrated in FIG. 9. An electronbeam emitted by the electronic gun is passed through the delay wavecircuit to amplify the signal and captured by the first collectorelectrode 42 and the second collector electrode 43.

[0015] For improving the efficiency of the traveling wave tube, there isusually employed a method of lowering the potential of the firstcollector electrode 42 to approximately 50% of that of the delay wavecircuit and of lowering the potential of the second collector electrode43 to approximately one-half that of the first collector electrode 42.This method consists in sequentially lowering the collector potentialwith respect to the potential of the delay wave circuit to lower thespeed of the electron beam impinging against the collector in order tolower the energy produced in each collector electrode while improvingthe overall efficiency of the traveling wave tube.

[0016] Referring to FIG. 9, in the case of a two-stage internalinsulation type collector 39, it is necessary to take out a firstcollector lead wire 45 of the first collector electrode 42 to a positionforwardly or rearwardly of the outer enclosure 41. In the present case,the collector lead wire is taken out to a position rearwardly of theouter enclosure 41 and is passed through the inside of an insulator tube46 for maintaining insulation of the first collector lead wire 45 toreduce the size of the collector. This insulator tube 46 is led torearwardly of the collector via a groove 47 formed in a portion of theouter periphery of the second collector electrode 43 so as to be led tooutside vacuum in an insulated state from a second collector lead line48.

[0017] In this structure, the electrical field is unavoidablyconcentrated in an edge portion of the insulator tube 46. Since there isa corner portion of the groove 47 in this edge portion, there is raiseda problem that the withstand voltage is deteriorated between the firstcollector lead line and the ground potential.

[0018] In addition to this structure, a demand is raised in recent yearsfor providing a small-sized lightweight structure easy to manufacturefor communication or loading on a satellite to lower the cost.

SUMMARY OF THE DISCLOSURE

[0019] The above-described collector structure of the conventionaltraveling wave tube is vulnerable to RF leakage from the collector leadline, such that, the RF power leakage occurs from the lead line portionif, in the case of the internal insulation type collector having aco-axial structure, impedance matching is taken between the collectorlead line and the collector inlet end.

[0020] Meanwhile, in JP Patent Kokai JP-A-4-306538 (1992), for example,there is disclosed a coupling cavity type traveling wave tube in which aloss member having loss in a high-impedance area and which is designedto suppress oscillations caused by the non-continuous coupling impedancein the high impedance area is arranged in the cavity. The conventionaltechnique of inserting this loss member is used in a high frequencycircuit system (cavity 49 in FIG. 10) because the loss member 50 is ofan electrically conductive material, as shown in the cross-sectionalview of FIG. 10.

[0021] It is therefore an object of the present invention to provide acollector of a traveling wave tube capable of maintainingvibration-proofness, impact-proofness and voltage withstandcharacteristics and yet capable of suppressing or eliminating RFleakage. for accomplishing the above object, the present inventionprovides a collector of an internal insulation type of a traveling wavetube having a structure in which a collector electrode is supported by aplurality of heat conductive columnar ceramic elements arranged betweenthe collector electrode and an outer enclosure of the collector, whereina loss ceramic member is arranged between the outer surface of thecollector electrode and the inner surface of the outer enclosure of thecollector.

[0022] Preferably, the loss ceramic member is cylindrically-shaped (orannular) and contacted at outer corners thereof with the outer enclosureof the collector. The loss ceramic member is contacted with thecollector electrode at its inner corner diagonally opposite to thecontacted portion thereof with the outer enclosure of the collector.

[0023] Preferably, the loss ceramic member(s) is (are) those on theouter peripheral surface of which is coated with a conductive layer suchas graphite coating.

[0024] As for the plural heat conductive columnar ceramic elements, anumber corresponding to the number of the collector electrodes less 1 ofthe columnar ceramic elements is designed as cylindrically-shapedceramic elements, if the number of the collector electrodes is two ormore. The cylindrically-shaped ceramic elements have a diameter equal toor less than the other heat conductive columnar ceramic elements. Thecylindrically-shaped ceramic elements are arranged in an area of thecollector electrode from which heat is most unlikely to be released.

[0025] Other features of the present invention are disclosed in theappended claims, the contents thereof being incorporated herein byreference thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1a is a transverse cross-sectional view of a collector of atraveling wave tube according to the present invention taken along lineA-A′ of FIG. 1(b), and

[0027]FIG. 1b is a longitudinal cross-sectional view taken along lineB-B′ of FIG. 1a.

[0028]FIG. 2 shows transmission characteristics (S21) of the collectorof a traveling wave tube according to the present invention andtransmission characteristics (S21) in the absence of loss ceramicelements as a comparative embodiment.

[0029]FIG. 3a is a transverse cross-sectional view of a secondembodiment according to the present invention taken along line A-A′ ofFIG. 3(b), and FIG. 3b is a longitudinal cross-sectional view takenalong line B-B′ of FIG. 1a.

[0030]FIG. 4 is a longitudinal cross-sectional view showing a structureof a conventional traveling wave tube of the conduction cooling type.

[0031]FIG. 5 is a longitudinal cross-sectional view showing a structureof a conventional traveling wave tube of the forced air cooling type.

[0032]FIG. 6 is a longitudinal cross-sectional view showing a structureof a conventional traveling wave tube of the water cooling type.

[0033]FIG. 7 is a longitudinal cross-sectional view showing an exampleof a conventional collector.

[0034]FIG. 8a is a transverse cross-sectional view of anotherconventional collector taken along line A-A′ of

[0035]FIG. 8b, and FIG. 8b is longitudinal cross-sectional view takenalong line B-B′ of FIG. 8a.

[0036]FIG. 9a is a transverse cross-sectional view of a two-stagecollector configuration and FIG. 9b is a longitudinal cross-sectionalview of FIG. 9b.

[0037]FIG. 10 is a transverse cross-sectional view of a cavity employinga conventional loss ceramic element.

PREFERRED EMBODIMENTS OF THE INVENTION

[0038] Preferred embodiments of the invention are explained further. Ina preferred embodiment of the present invention, there is provided aninternal insulating collector of the type in which a collector electrode(2 of FIG. j) is supported by plural heat conductive columnar ceramicelements (3 of FIG. 1) arranged between the electrode and an outerenclosure (4 of FIG. 1), in which loss ceramic members displayingsignificant loss (high frequency loss or dielectric loss) and superiorinsulating properties (5 of FIG. 1) are arranged between the outersurface of the collector electrode (surface not illuminated with anelectron beam) and the inner surface of the outer enclosure of thecollector (surface contacting with insulating ceramics). This lossceramic members may be those on the outer peripheral surface of which iscoated with e.g., Aquadag (7 of FIG. 1).

[0039] Preferably, according to a preferred embodiment of the presentinvention, the loss ceramic members are cylindrically-shaped (annularring), the outer diametrical portion of each loss ceramic membercontacts with the outer enclosure of the collector and the corner of theinner diametrical portion of the loss ceramic member disposeddiametrically to the contacting portion contacts with the collectorelectrode. This realizes axial positioning of the collector whilemaintaining vibration-proofness and impact-proofness.

[0040] Among the plural heat conductive columnar ceramic elements, anumber corresponding to the number of the collector electrodes less 1 ofthe columnar ceramic elements are designed as cylindrically-shaped (e.g,hollow) ceramic element(s), if the number of the collector electrodes istwo or more. These cylindrically-shaped ceramic element(s) has adiameter equal to or smaller than the other heat conductive columnarceramic elements. For improving voltage withstand characteristics, thesecylindrically-shaped ceramic elements are disposed without any grooveformed in the second collector (on the outer periphery thereof) forlaying conventional insulating tubes as in the conventional collector.Meanwhile, the cylindrically-shaped ceramic element(s) is positioned inan area from which heat of the collector electrode is most unlikely tobe released (or dissipated), for example, on the opposite side to thebase plate in case of conduction cooling, towards the base plate in caseof the forced air cooling, and in an area of lesser congestion ofwater-cooling pipes in case of forced water cooling.

[0041] With the collector of the present embodiment of the presentinvention, in which loss ceramic members superior in insulationproperties are arranged forwardly and rearwardly of the collector forpreventing RF leakage from the collector, and collector lead wire ispassed through the inside of the cylindrically-shaped (hollow) heatconductive columnar ceramic elements designed for collector insulation,voltage withstand characteristics can be improved whilevibration-proofness and impact-proofness equivalent to those in theconventional system are maintained, and also RF leakage may be preventedfrom occurring from the collector.

[0042] Embodiments

[0043] Referring to the drawings, preferred embodiments of the presentinvention will be explained in detail.

[0044] [First Embodiment]

[0045]FIG. 1 shows a collector structure of a traveling wave tube (orguide) embodying the present invention. Specifically, FIG. 1a is atransverse cross-sectional view of an internal insulating type collectorof a traveling wave tube and FIG. 1b is a longitudinal cross-sectionalview taken along line B-B′ of FIG. 1a.

[0046] Referring to FIG. 1, a collector 1 of a traveling wave tube ofthe preset embodiment is made up of a collector electrode 2, heatconductive columnar ceramic elements 3, an outer enclosure 4 formaintaining vacuum and loss ceramic members 5 provided forwardly orrearwardly of the collector electrode 2.

[0047] The heat conductive columnar ceramic elements 3 are axiallyarranged (distributed) over the entire area (circumference) of anannular gap defined between the outer peripheral surface of thecylindrically-shaped collector electrode 2 and the inner peripheralsurface of the cylindrically-shaped outer enclosure 4. The heatconductive columnar ceramic elements o are kept in contact with thecollector electrode 2 by an outer flange thereof so that the ceramicelements 3 are not deflected at their axial ends. For improving voltagewithstand characteristics, the inner peripheral surface of the outerenclosure 4 is spaced apart at the axial end portions from the heatconductive columnar ceramic element 3 by annular gaps 6, 6 of severalmm. As a matter of course, the broader this gap, the lesser is thedegree of concentration of the electrical field and the higher arevoltage withstand characteristics.

[0048] Also, there is a small axial clearance between the columnarceramic elements 3 and the rear loss ceramic member 5, which in turn isaxially secured on a shoulder formed at the outer peripheral corner ofthe end plate of outer enclosure 4 leaving an axial clearance. Theforward loss ceramic member 5 is axially and radially secured by aninward flange formed within the outer enclosure 4, while the diagonallyopposite corner of the loss ceramic member 5 is axially secured by theoutward flange at the forward end of the collector electrode 2. The rearloss ceramic member 5 is radially secured on a small annular rib orprotrusions axially extending from the rear end of the collectorelectrode 2.

[0049] The cylindrically-shaped (annular ring) loss ceramic members 5are arranged at both ends of the heat conductive columnar ceramicelements 3 so that a portion of the inner surface of each member 5 iscontacted with (secured by) the collector electrode 2 and the corner ofthe outer surface of the loss ceramic member lying diagonally oppositeto the contacted portion with the collector electrode 2 is contactedwith (secured by) the outer enclosure.

[0050] The loss ceramic members 5 are of alumina material etc. coated onouter sides with a graphite layer of Aquadag E (trade name of NihonAtisson K.K., a mixture of graphite and an aqueous binder).

[0051] After assembling the above structure of the entire collector, theresulting assembly is pressed from outside such as press-working to takeheat conduction into account to deform the outer enclosure 4 to securethe various components in situ.

[0052]FIG. 2 shows characteristics 8 as a transmission circuit (S21) inthe TEM mode of the collector 1 of the structure of the presetembodiment. FIG. 2 shows, as a comparative embodiment, transmissioncharacteristics 9 (S21) in the absence of the loss ceramic members 5.

[0053] As a measurement method, RF signals were entered at an electronbeam incident end of the collector 1 and the signal level thereof wasmeasured from a collector terminal 11 connecting to a collector leadwire 10. As may be seen from FIG. 2, the signal level was improved byapproximately 20 dB in the present embodiment.

[0054] It may be surmised that the forward side loss ceramic memberaccounts for a loss of 10 dB, while the rear side loss ceramic memberaccounts for a loss of 10 dB, thus achieving improvement of 20 dB.

[0055] [Second Embodiment]

[0056] As a second embodiment, an internal insulation type two-stagedcollector is explained.

[0057]FIG. 3 shows the collector structure of the second embodiment ofthe present invention. Specifically, FIG. 3a is a transversecross-sectional view of the collector structure and FIG. 3b is alongitudinal cross-sectional view taken along line A-A′ thereof.

[0058] Referring to FIG. 3, the second embodiment of the presentinvention includes a first collector electrode 13, a second collectorelectrode 14, highly heat conductive columnar ceramic elements 15, anouter enclosure 16 for maintaining vacuum, loss ceramic members 17,arranged forwardly of the first collector electrode 13 and rearwardly ofthe second collector electrode 14, a first collector lead wire 18extending from the first collector electrode 13 along the outerperipheral surface of the second collector electrode 14 to the rear sideof the second collector via a cylindrically-shaped (hollow) ceramicelement 19 for maintaining the insulation of the collector lead wire.

[0059] The first and second loss ceramic members 17 are axially securedbetween flanges formed on the collector electrodes 13, 14 and outerenclosure 16. Namely, the forward loss ceramic member 17 is securedbetween an inward protruding flange of the outer enclosure 16 and theoutward protruding flange at the forward end of the first collectorelectrode 13. The rearward loss ceramic member is secured between theinward protruding flange of the outer enclosure 16 and the outwardflange at the rear end of the second collector electrode 14. Thecolumnar ceramic elements are axially secured between two outwardflanges of the first and second collector electrodes 13, 14.

[0060] The first collector lead wire 18 is led to outside vacuum via afirst collector terminal 20. In addition, a second collector lead wire21 is led to outside vacuum via a second collector terminal 22.

[0061] The first collector lead wire 18 is passed through the inside ofcylindrically-shaped ceramic elements 19, placed in lieu of the heatconductive columnar ceramic elements 15, so as to be led to the rearside of the collector. The outer diameter of the cylindrically-shapedceramic elements 19 is equal to or less than the diameter of the heatconductive columnar ceramic elements.

[0062] If the collector cooling method is of the conduction coolingtype, the collector is placed on the opposite side of a portion of abase plate where the collector is contacted with a heat sink, that is onthe side where heat dissipation is at the least level. If the collectorcooling method is of the forced air cooling type or the water coolingtype, the collector is placed on the side of the base plate carrying thecollector where there is no air or water flow, that is towards the baseplate carrying the collector. In short, the collector position isdirectly opposite to the conduction cooling position.

[0063] The present embodiment has an advantage that voltage withstandcharacteristics, vibration-proofness or impact-proofness and heatconductivity are equivalent to those of the first embodiment, eventhough the number of the collector stages is increased, thus assuringfacilitated multi-stage collector designing.

[0064] It is noted that the Aquadag can be applied not only on the outerperipheral surfaces but also on the inner peripheral surfaces of theloss ceramic elements. Moreover, Aquadag can be applied to both surfacesof the loss ceramic elements if voltage withstand characteristicspermit. Alternatively, Aquadag can be applied to a portion of thesurfaces of the loss ceramic elements depending on the amount of RFleakage.

[0065] The meritorious effects of the present invention are summarizedas follows.

[0066] According to the present invention, as described above, there maybe provided an internal insulation type collector in which, by placingloss ceramic elements on the collector, RF leakage from the collectormay be prevented and axial position setting can also be achieved whilevibration-proofness and impact-proofness equivalent to those of theconventional system are maintained, and yet the voltage withstandcharacteristics can be improved.

[0067] Moreover, according to the present invention, high heatconductivity and voltage withstand characteristics can be maintained inachieving multi-stage collecting designing in consideration ofarrangement of the collector lead wires.

[0068] The present invention may be used in combination with otherstructures and elements of the conventional devices other than thespecific features of the present invention. Thus the entire disclosurerelating to the prior art is also incorporated by reference in thedisclosure of the present invention.

[0069] Further any arbitrary combination of the disclosed featuresand/or elements may be done within the gist of the present inventionirrespective of the place of disclosure including the entire claims.

[0070] It should be noted that other objects of the present inventionwill become apparent in the entire disclosure and that modifications maybe done without departing the gist and scope of the present invention asdisclosed herein and appended herewith.

What is claimed is:
 1. A collector of an internal insulation type of atraveling wave tube having a structure in which a collector electrode issupported by a plurality of heat conductive columnar ceramic elementsarranged between the collector electrode and an outer enclosure of thecollector, wherein a loss ceramic member is arranged between the outersurface of the collector electrode and the inner surface of the outerenclosure of the collector.
 2. The collector of the traveling wave tubeas defined in claim 1 , wherein said loss ceramic member iscylindrically-shaped and contacted at outer corners thereof with theouter enclosure of the collector, said loss ceramic member beingcontacted with said collector electrode at its inner corner diagonallyopposite to the contacted portion thereof with the outer enclosure ofthe collector.
 3. The collector of the traveling wave tube as defined inclaim 1 , wherein said loss ceramic member is coated with a conductivelayer at least a portion of the surface thereof.
 4. The collector of thetraveling wave tube as defined in claim 3 , wherein said conductivelayer is coated on the outer peripheral surface of said loss ceramicmember.
 5. The collector of the traveling wave tube as defined in claim1 , wherein among the plural heat conductive columnar ceramic elements,a number corresponding to the number of the collector electrodes less 1of the columnar ceramic elements is designed as cylindrically-shapedhollow ceramic elements, if the number of the collector electrodes istwo or more, said cylindrically-shaped hollow ceramic element has adiameter equal to or less than the other heat conductive columnarceramic elements, and wherein said cylindrically-shaped hollow ceramicelement is arranged in an area of the collector electrode from whichheat is most unlikely to be released.
 6. A collector of an internalinsulation type of a traveling wave tube having a structure in which acollector electrode is supported by a plurality of heat conductivecolumnar ceramic elements arranged between the collector electrode andan outer enclosure of the collector, wherein insulating loss ceramicmembers displaying high frequency loss are arranged between the outersurface of said collector electrode not illuminated with an electronbeam and a surface of said outer enclosure contacted with said columnarceramic elements.
 7. The collector of the traveling wave tube as definedin claim 6 , wherein said loss ceramic members are in the form of ahollow cylinder, the outer diametrical portion of which is contacted onone side of said cylinder with said outer enclosure, and the innerdiametrical portion of which is contacted on the other side of saidcylinder with said collector electrode.
 8. The collector of thetraveling wave tube as defined in claim 6 , wherein a pair of said lossceramic members are disposed at the forward and rear ends of thecollector electrode or a collector electrode assembly.
 9. The collectorof the traveling wave tube as defined in claim 8 , wherein saidcollector electrode assembly includes two collector electrodes disposedaxially thereof.
 10. The collector of the traveling wave tube as definedin claim 6 , wherein said loss ceramic member is secured by a flange orflanges formed on the collector electrode and/or the collectorelectrode.
 11. The collector of the traveling wave tube as defined inclaim 6 , wherein there is a gap between at least one end of thecolumnar ceramic elements and the outer enclosure.
 12. The collector ofthe traveling wave tube as defined in claim 11 , wherein said gap isannularly and axially extends also over the radially outer area of theloss ceramic member.
 13. The collector of the traveling wave tube asdefined in claim 9 , wherein at least one of said loss ceramic membersis secured between a flange formed on one of the collector electrodesand a flange formed on the outer enclosure.
 14. The collector of thetraveling wave tube as defined in claim 6 , wherein the loss ceramicmember is disposed between said collector electrode and said outerenclosure with a least contact area sufficient for securing,respectively, otherwise leaving a clearance or gap with said collectorelectrode and said outer enclosure.